org.jets3t.service.io.InterruptableInputStream.java Source code

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Here is the source code for org.jets3t.service.io.InterruptableInputStream.java

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/*
 * JetS3t : Java S3 Toolkit
 * Project hosted at http://bitbucket.org/jmurty/jets3t/
 *
 * Copyright 2006-2010 James Murty
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.jets3t.service.io;

import java.io.IOException;
import java.io.InputStream;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Input stream wrapper that allows the underlying wrapped input stream to be interrupted.
 * Every time a blocking stream operation is invoked on this class, the interrupt flag is
 * checked first. If this flag is set, the underlying stream is closed and an IOException
 * "Input Stream Interrupted" is thrown.
 * <p>
 * <b>Note</b>: This hacky class does not really solve the problem of interrupting blocking
 * Java input streams, as it cannot unblock a blocked read operation. It really just serves
 * as a convenient way to interrupt streams before any potentially blocking operations.
 *
 * @author James Murty
 */
public class InterruptableInputStream extends InputStream implements InputStreamWrapper {
    private static final Log log = LogFactory.getLog(InterruptableInputStream.class);

    private InputStream inputStream = null;

    private boolean interrupted = false;

    public InterruptableInputStream(InputStream inputStream) {
        this.inputStream = inputStream;
    }

    private void maybeInterruptInputStream() throws IOException {
        if (interrupted) {
            if (log.isDebugEnabled()) {
                log.debug(
                        "Input stream interrupted, closing underlying input stream " + this.inputStream.getClass());
            }
            try {
                close();
            } catch (IOException ioe) {
                if (log.isWarnEnabled()) {
                    log.warn("Unable to close underlying InputStream on interrupt");
                }
            }
            // Throw an unrecoverable exception to indicate that this exception was deliberate, and
            // should not be recovered from.
            throw new UnrecoverableIOException("Reading from input stream deliberately interrupted");
        }
    }

    @Override
    public int read() throws IOException {
        maybeInterruptInputStream();
        return inputStream.read();
    }

    @Override
    public int read(byte[] b, int off, int len) throws IOException {
        maybeInterruptInputStream();
        return inputStream.read(b, off, len);
    }

    @Override
    public int available() throws IOException {
        maybeInterruptInputStream();
        return inputStream.available();
    }

    @Override
    public void close() throws IOException {
        inputStream.close();
    }

    public InputStream getWrappedInputStream() {
        return inputStream;
    }

    public void interrupt() {
        interrupted = true;
    }

}